The recent growth in many areas of biotechnology has increased the demand to perform a variety of studies, commonly referred to as assays, of biological and chemical systems. These assays include for example, biochemical reaction kinetics, DNA melting point determinations, DNA spectral shifts, DNA and protein concentration measurements, excitation/emission of fluorescent probes, enzyme activities, enzyme co-factor assays, homogeneous assays, drug metabolite assays, drug concentration assays, dispensing confirmation, volume confirmation, solvent concentration, and solvation concentration. Also, there are a number of assays which use intact living cells and which require visual examination.
Assays of biological and chemical systems are carried out on a large scale in both industry and academia, so it is desirable to have an apparatus that allows these assays to be performed in convenient and inexpensive fashion. Because they are relatively easy to handle, are low in cost, and generally disposable after a single use, multiwell plates, which are also called microplates, are often used for such studies. Multiwell plates typically are formed from a polymeric material and consist of an ordered array of individual wells. Each well includes sidewalls and a bottom so that an aliquot of sample may be placed within each well. The wells may be arranged in a matrix of mutually perpendicular rows and columns. Common sizes for multiwell plates include matrices having standardized dimensions of approximately 85 mm×128 mm with well capacities of 8×12 (96 wells), 16×24 (384 wells), and 32×48 (1536 wells).
Evaporation of the liquid contained in wells of multiwell plates with a conventional solid lid, especially multiwell plates with well capacities of 1536 wells or higher, within an incubator or on the countertop can exceed 15% to 25% in the corner wells and the wells on the outer periphery of the plate. The high amount evaporation from these wells of these plates causes dramatic changes in pH, nutrients, salt concentrations, etc. and cause what is called “the edge effect,” especially when cell based assays are performed.
Sealing tapes or films with necessary air and gas exchange have been used to prevent bulk evaporation as well as the edge effect. Examples of these products include Aeraseal™ Sealing Films and Breathe-Easy™ gas permeable sealing membranes for microtiter plates available from Diversified Biotech, Boston, Mass. However, such films are not automation friendly with the high throughput screening (HTS) procedures used in many laboratories. A commercially available device, Modular Incubator Chamber, was developed to eliminate the edge effect. Nine 96-well plates can be put in the chamber with customized tissue culturing conditions. One drawback to the device is that it has to be manually operated and does not meet high throughput screening requirements.
There is a need to provide a multiwell plate lid that can reduce or eliminate the edge effect. It would be desirable to provide a lid that is inexpensive to manufacture and is compatible with HTS screening requirements